1 # __str__ __repr__
2 # %s str() %r repr()
3 # class A:
4 # def __init__(self,name):
5 # self.name = name
6 # def __str__(self):
7 # return self.name
8 # # def __repr__(self):
9 # # return self.name
10 # a = A('alex')
11 # str(a)---->a.__str__()
12 # repr(a)----> a.__repr()
13 # print(str(a)) # alex
14 # print(repr(a)) # <__main__.A object at 0x00000232AD2F9710>
15
16 # object 里有一个__str__,一旦被调用，就返回调用这个方法的对象的内存地址
17 # repr是str的备胎，但str不能做repr的备胎
18 # print(obj)/'%s'%obj/str(obj)的时候，实际上是内部调用了obj.__str__方法，如果str方法有，那么他返回的必定是一个字符串
19 # 如果没有__str__方法，会先找本类中的__repr__方法，再没有再找父类中的__str__。
20 # repr(),只会找__repr__,如果没有找父类的
21
22 # 内置的方法有很多
23 # 不一定全都在object中
24
25 # __len__ __call__
26 # class A:
27 # def __len__(self):
28 # return 10
29 # def __call__(self, *args, **kwargs):
30 # print('in the call')
31 #
32 # a = A()
33 # print(len(a))
34 # a() # 对象()的方式相当于调用了对象的__call__方法
35
36 # __del__
37 # class A:
38 # def __del__(self): # 析构函数在删除对象前进行一些收尾工作
39 # self.f.close()
__new__
1 # __new__
2 # class A:
3 # def __init__(self):
4 # self.x = 1
5 # print('in init function')
6 # def __new__(cls, *args, **kwargs):
7 # print('in new function')
8 # return object.__new__(cls)
9 # a = A()
10 # print(a.x)
11 # # 先执行new方法，new创建了一个self对象传给了init方法
12 # # 输出：
13 # # in new function
14 # # in init function
15 # # 1
__eq__和__hash__
1 # __eq__ __hash__
2 # class A:
3 # def __init__(self):
4 # self.a = 1
5 # self.b = 2
6 # def __eq__(self, other):
7 # if self.a == other.a and self.b == other.b:
8 # return True
9 # a = A()
10 # b = A()
11 # print(a==b)
12 # print(a is b)
13
14
15 # class Person:
16 # def __init__(self,name,age,sex):
17 # self.name = name
18 # self.age = age
19 # self.sex = sex
20 # def __str__(self):
21 # return str([self.name,self.age,self.sex])
22 #
23 # # 如果没有实现hash方法会报错：TypeError: unhashable type: 'Person'
24 # def __hash__(self):
25 # print('in hash')
26 # return hash(self.name+self.sex)
27 #
28 # def __eq__(self, other):
29 # print('in eq')
30 # if self.name == other.name and self.sex == other.sex:return True
31 #
32 # p_lst = []
33 # for i in range(10):
34 # p_lst.append(Person('egon',i,'male'))
35 # for i in p_lst:
36 # print(i,end=' ')
37 # # set 去重，需要实现__hash__ 和 __eq__ 方法，先执行hash，后执行eq
38 # p_lst2 = list(set(p_lst))
39 # print()
40 # for i in p_lst2:
41 # print(i,end=' ')
关于set去重
# 用set对列表去重并保持原来顺序
# mailto = ['cc', 'bbbb', 'afa', 'sss', 'bbbb', 'cc', 'shafa']
# addr_to = list(set(mailto))
# print(addr_to)
# a = sorted(addr_to,key=mailto.index)
# print(a)
# # addr_to.sort(key = mailto.index)
# print(addr_to)
__getitem__ __setitem__ __delitem__
1 # class Foo:
2 # def __init__(self,name,age,sex):
3 # self.name = name
4 # self.age = age
5 # self.sex = sex
6 #
7 # def __getitem__(self, item):
8 # if hasattr(self,item):
9 # return self.__dict__[item]
10 #
11 # def __setitem__(self, key, value):
12 # self.__dict__[key] = value
13 #
14 # def __delitem__(self, key):
15 # del self.__dict__[key]
16 #
17 # f = Foo('egon',38,'男')
18 # # print(f['name'])
19 # f['hobby'] = '男'
20 # print(f.hobby)
21 # # print(f.hobby,f['hobby'])
22 # # del f['hobby']
23 # # del f.hobby # object 原生支持 __delattr__
24 # # del f['hobby'] # 通过自己实现的
25 # # print(f.__dict__)
